High-power laser systems with modular diode sources

ABSTRACT

In various embodiments, a modular laser system features an enclosure having interfaces for accepting input laser beam modules, optical elements for combining beams from the modules into a combined output beam, and a heat-exchange manifold for interfacing with and cooling the modules during operation.

RELATED APPLICATION

This application claims the benefit of and priority to U.S. ProvisionalPatent Application No. 62/371,341, filed Aug. 5, 2016, the entiredisclosure of which is hereby incorporated herein by reference.

TECHNICAL FIELD

In various embodiments, the present invention relates to high-powerlaser systems having modular beam sources.

BACKGROUND

High-power laser systems are utilized for a host of differentapplications, such as welding, cutting, drilling, and materialsprocessing. Such laser systems typically include a laser emitter, thelaser light from which is coupled into an optical fiber (or simply a“fiber”), and an optical system that focuses the laser light from thefiber onto the workpiece to be processed. Wavelength beam combining(WBC) is a technique for scaling the output power and brightness fromlaser diodes, laser diode bars, stacks of diode bars, or other lasersarranged in a one- or two-dimensional array. WBC methods have beendeveloped to combine beams along one or both dimensions of an array ofemitters. Typical WBC systems include a plurality of emitters, such asone or more diode bars, that are combined using a dispersive element toform a multi-wavelength beam. Each emitter in the WBC systemindividually resonates, and is stabilized through wavelength-specificfeedback from a common partially reflecting output coupler that isfiltered by the dispersive element along a beam-combining dimension.Exemplary WBC systems are detailed in U.S. Pat. No. 6,192,062, filed onFeb. 4, 2000, U.S. Pat. No. 6,208,679, filed on Sep. 8, 1998, U.S. Pat.No. 8,670,180, filed on Aug. 25, 2011, and U.S. Pat. No. 8,559,107,filed on Mar. 7, 2011, the entire disclosure of each of which isincorporated by reference herein.

While techniques such as WBC have succeeded in producing laser-basedsystems for a wide variety of applications, wider adoption of suchsystems has resulted in the demand for ever-higher levels of laseroutput power. High-power laser systems such as WBC systems and/orfiber-coupled laser systems are quite complex and may therefore be quiteexpensive; therefore, reliability is a key metric for such systems. Manyhigh-power laser systems utilize solid-state laser diode (or simply“diode”) sources that are deeply integrated within the laser system;thus, reliability and cost of ownership of such systems is limited bythe fact that the diode sources typically cannot be replaced in thefield in the event of diode failure. Therefore, there is a need forhigh-power laser systems in which diode laser sources are more easilyreplaced or repaired, thereby improving system up-time and decreasingoverall costs.

SUMMARY

In accordance with embodiments of the present invention, high-powerlaser systems feature multiple individually replaceable laser sourcemodules each containing at least one laser source, e.g., one or morediode-based sources. The source modules may be removed from the systemand replaced “in the field” by the end user, improving systemreliability and operation time. In addition, the replaceable modules maybe driven at higher currents, given their replaceability. Although insome embodiments such high current drive may result in earlier failureof individual diode sources, higher-current operation may enable systemsin accordance with embodiments of the invention to utilize fewer sources(e.g., 20%-50% fewer sources), and may thus be correspondingly lessexpensive.

Laser source modules in accordance with embodiments of the invention mayfeature electrical and optical interfaces that interface withcomplementary features on a beam-combining enclosure in which theindividual beams from the modules are combined into a single output beam(and, in some embodiments, coupled into an optical fiber). These opticaland electrical interfaces facilitate the easy replacement of input lasersources with a minimal amount, if any, of associated alignment of thesource. Systems in accordance with embodiments of the invention alsofeature modular heat-exchange manifolds that are easily connectable toand disconnectable from any desired number of laser sources utilized inthe system. The source modules are insertable into and interface withinput receptacles disposed in or on the enclosure in which the inputbeams are combined to form the output beam.

Laser devices in accordance with embodiments of the present inventionmay be utilized in WBC systems to form high brightness, low beamparameter product (BPP) laser systems. The BPP is the product of thelaser beam's divergence angle (half-angle) and the radius of the beam atits narrowest point (i.e., the beam waist, the minimum spot size). TheBPP quantifies the quality of the laser beam and how well it can befocused to a small spot, and is typically expressed in units ofmillimeter-milliradians (mm-mrad). A Gaussian beam has the lowestpossible BPP, given by the wavelength of the laser light divided by pi.The ratio of the BPP of an actual beam to that of an ideal Gaussian beamat the same wavelength is denoted M², or the “beam quality factor,”which is a wavelength-independent measure of beam quality, with the“best” quality corresponding to the “lowest” beam quality factor of 1.

As utilized herein, materials with a high thermal conductivity, or“thermally conductive materials,” have a thermal conductivity of atleast 100 watts per meter per Kelvin (W·m⁻¹·K⁻¹), at least 170W·m⁻¹·K⁻¹, or even at least 300 W·m⁻¹·K⁻¹. As utilized herein, materialswith a high electrical conductivity, or “electrically conductivematerials,” have an electrical conductivity, e.g., at 20° C., of atleast 1×10⁵ siemens per meter (S/m), at least 1×10⁶ S/m, or even atleast 1×10⁷ S/m. As utilized herein, materials with a high electricalresistivity, or “electrically insulating materials,” have an electricalresistivity of at least 1×10⁸ ohm·meter (Ω·m), at least 1×10¹⁰ Ω·m, oreven at least 1×10¹² Ω·m.

As known to those of skill in the art, lasers are generally defined asdevices that generate visible or invisible light through stimulatedemission of light. Lasers generally have properties that make themuseful in a variety of applications, as mentioned above. Common lasertypes include semiconductor lasers (e.g., laser diodes and diode bars),solid-state lasers, fiber lasers, and gas lasers. A laser diode isgenerally based on a simple diode structure that supports the emissionof photons (light). However, to improve efficiency, power, beam quality,brightness, tunability, and the like, this simple structure is generallymodified to provide a variety of many practical types of laser diodes.Laser diode types include small edge-emitting varieties that generatefrom a few milliwatts up to roughly half a watt of output power in abeam with high beam quality. Structural types of diode lasers includedouble hetero-structure lasers that feature a layer of low bandgapmaterial sandwiched between two high bandgap layers; quantum well lasersthat include a very thin middle (quantum well) layer resulting in highefficiency and quantization of the laser's energy; multiple quantum welllasers that include more than one quantum well layer to improve gaincharacteristics; quantum wire or quantum sea (dots) lasers that replacethe middle layer with a wire or dots to produce higher-efficiencyquantum well lasers; quantum cascade lasers that enable laser action atrelatively long wavelengths that may be tuned by altering the thicknessof the quantum layer; separate confinement heterostructure lasers, whichare the most common commercial laser diode and include another twolayers above and below the quantum well layer to efficiently confine thelight produced; distributed feedback lasers, which are commonly used indemanding optical communication applications and include an integrateddiffraction grating that facilitates generating a stable wavelength setduring manufacturing by reflecting a single wavelength back to the gainregion; vertical-cavity surface-emitting lasers (VCSELs), which have adifferent structure that other laser diodes in that light is emittedfrom its surface rather than from its edge; and vertical-external-cavitysurface-emitting lasers (VECSELs) and external-cavity diode lasers,which are tunable lasers that use mainly double heterostructure diodesand include gratings or multiple-prism grating configurations.External-cavity diode lasers are often wavelength-tunable and exhibit asmall emission line width. Laser diode types also include a variety ofhigh power diode-based lasers including: broad area lasers that arecharacterized by multi-mode diodes with oblong output facets andgenerally have poor beam quality but generate a few watts of power;tapered lasers that are characterized by astigmatic mode diodes withtapered output facets that exhibit improved beam quality and brightnesswhen compared to broad area lasers; ridge waveguide lasers that arecharacterized by elliptical mode diodes with oval output facets; andslab-coupled optical waveguide lasers (SCOWL) that are characterized bycircular mode diodes with output facets and may generate watt-leveloutput in a diffraction-limited beam with nearly a circular profile.

A diode-laser bar is a type of semiconductor laser containing aone-dimensional array of broad-area emitters or alternatively containingsub arrays containing, e.g., 10-20 narrow stripe emitters. A broad-areadiode bar typically contains, for example, 19-49 emitters, each havingdimensions on the order of, e.g., 1 μm×100 μm. The beam quality alongthe 1 μm dimension or fast-axis is typically diffraction-limited. Thebeam quality along the 100 μm dimension or slow-axis or array dimensionis typically many times diffraction-limited. Typically, a diode bar forcommercial applications has a laser resonator length of the order of 1to 4 mm, is about 10 mm wide and generates tens of watts of outputpower. Most diode bars operate in the wavelength region from 780 to 1070nm, with the wavelengths of 808 nm (for pumping neodymium lasers) and940 nm (for pumping Yb:YAG) being most prominent. The wavelength rangeof 915-976 nm is used for pumping erbium-doped or ytterbium-dopedhigh-power fiber lasers and amplifiers.

Embodiments of the present invention couple the one or more laser beams(e.g., emitted by laser devices packaged as detailed herein) into anoptical fiber. In various embodiments, the optical fiber has multiplecladding layers surrounding a single core, multiple discrete coreregions (or “cores”) within a single cladding layer, or multiple coressurrounded by multiple cladding layers.

Herein, “optical elements” may refer to any of lenses, mirrors, prisms,gratings, and the like, which redirect, reflect, bend, or in any othermanner optically manipulate electromagnetic radiation. Herein, beamemitters, emitters, or laser emitters, or lasers include anyelectromagnetic beam-generating device such as semiconductor elements,which generate an electromagnetic beam, but may or may not beself-resonating. These also include fiber lasers, disk lasers, non-solidstate lasers, etc. Generally, each emitter includes a back reflectivesurface, at least one optical gain medium, and a front reflectivesurface. The optical gain medium increases the gain of electromagneticradiation that is not limited to any particular portion of theelectromagnetic spectrum, but that may be visible, infrared, and/orultraviolet light. An emitter may include or consist essentially ofmultiple beam emitters such as a diode bar configured to emit multiplebeams. The input beams received in the embodiments herein may besingle-wavelength or multi-wavelength beams combined using varioustechniques known in the art. In addition, references to “lasers,” “laseremitters,” or “beam emitters” herein include not only single-diodelasers, but also diode bars, laser arrays, diode bar arrays, and singleor arrays of vertical cavity surface-emitting lasers (VCSELs).

In an aspect, embodiments of the invention feature a laser system forcombining a plurality of input beams into a combined output beam. Thelaser system includes, consists essentially of, or consists of anenclosure, a heat-exchange manifold, a plurality of input beam modules,a plurality of input receptacles disposed on the enclosure, and aplurality of optical elements disposed within the enclosure. Theenclosure includes a beam output for outputting the combined outputbeam. The heat-exchange manifold includes, consists essentially of, orconsists of (i) a reservoir for containing heat-exchange fluid, and (ii)a plurality of heat-exchange interfaces each including, consistingessentially of, or consisting of (a) an output conduit for supplyingheat-exchange fluid and (b) an input conduit for receiving heat-exchangefluid. Each input module includes, consists essentially of, or consistsof (i) a housing, (ii) a laser beam source disposed within the housing,(iii) disposed within the housing, a focusing optical element forreceiving and focusing one or more input beams emitted by the laser beamsource, (iv) disposed on the housing, an optical interface fortransmitting the focused one or more input beams out of the housing, (v)disposed on the housing, an electrical interface for transmittingelectrical power into the housing and to the laser beam source, and (vi)a cooling interface comprising (a) a cooling input for receivingheat-exchange fluid from one of the output conduits of the heat-exchangemanifold and disposing the heat-exchange fluid in thermal contact withthe laser beam source and (b) a cooling output for receivingheat-exchange fluid from the laser beam source after heat exchangetherebetween and outputting the heat-exchange fluid to an input conduitof the heat-exchange manifold. Each input receptacle is configured toaccept one of the input beam modules. Each input beam receptacleincludes, consists essentially of, or consists of (i) an electricaloutput for supplying electrical power, (ii) an optical receiver forreceiving one or more input beams from an input beam module, and (iii)an alignment feature for mechanically aligning an input beam module withthe enclosure, whereby, when an input beam module is accepted within theinput beam receptacle, the electrical output is electrically connectedto the electrical interface of the input beam module and the opticalreceiver is optically aligned with the optical interface of the inputbeam module. The optical elements disposed within the enclosure receiveinput beams from the optical receivers of the input receptacles, combinethe input beams into a combined output beam, and transmit the combinedoutput beam to the beam output.

Embodiments of the invention may include one or more of the following inany of a variety of combinations. The beam output may include, consistessentially of, or consist of an output receptacle for receiving anoptical fiber. An optical fiber may be coupled to the beam output. Thebeam output may include, consist essentially of, or consist of a window(e.g., an opening or a solid member substantially transparent to theoutput beam) for transmitting a free-space output beam. One or more, oreven all, of the laser beam sources may include, consist essentially of,or consist of a diode bar configured to emit a plurality of laser beams.The plurality of optical elements disposed within the enclosure mayinclude, consist essentially of, or consist of (i) focusing optics forfocusing input beams onto a dispersive element, (ii) a dispersiveelement for receiving and dispersing the received focused input beams,and (iii) a partially reflective output coupler positioned to receivethe dispersed beams, transmit a portion of the dispersed beamstherethrough as the combined output beam, and reflect a second portionof the dispersed beams back toward the dispersive element. The pluralityof optical elements disposed within the enclosure may include, consistessentially of, or consist of focusing optics for focusing input beamsonto or proximate the beam output. The dispersive element may include,consist essentially of, or consist of a diffraction grating (e.g., atransmissive grating or a reflective grating). The optical elements maybe configured to combine the input beams into the combined output beamand transmit the combined output beam to the beam output even if one ormore of the input receptacles is empty. The laser system may include acontrol system configured to control flow of heat-exchange fluid througheach of the heat-exchange interfaces. The control system may beconfigured to control the flow of heat-exchange fluid based at least inpart on a sensed temperature of each of the input beam modules. Theoptical interface of at least one of the input beam modules may include,consist essentially of, or consist of a window, prism, and/or lens. Theoptical receiver of at least one of the input receptacles may include,consist essentially of, or consist of a window, prism, and/or lens.

In another aspect, embodiments of the invention feature a laser systemfor combining a plurality of input beams emitted by a plurality of inputbeam modules into a combined output beam. Each of the input beam modulesincludes, consists essentially of, or consists of (i) a housing, (ii) alaser beam source disposed within the housing, (iii) disposed within thehousing, a focusing optical element for receiving and focusing one ormore input beams emitted by the laser beam source, (iv) disposed on thehousing, an optical interface for transmitting the focused one or moreinput beams out of the housing, (v) disposed on the housing, anelectrical interface for transmitting electrical power into the housingand to the laser beam source, and (vi) a cooling interface comprising(a) a cooling input for receiving heat-exchange fluid and disposing theheat-exchange fluid in thermal contact with the laser beam source and(b) a cooling output for receiving heat-exchange fluid from the laserbeam source after heat exchange therebetween and outputting theheat-exchange fluid. The laser system includes, consists essentially of,or consists of an enclosure, a heat-exchange manifold, a plurality ofinput receptacles disposed on the enclosure, and a plurality of opticalelements disposed within the enclosure. The enclosure includes a beamoutput for outputting the combined output beam. The heat-exchangemanifold includes, consists essentially of, or consists of (i) areservoir for containing heat-exchange fluid, and (ii) a plurality ofheat-exchange interfaces each including, consisting essentially of, orconsisting of (a) an output conduit for supplying heat-exchange fluid toa cooling input of one of the input beam modules and (b) an inputconduit for receiving heat-exchange fluid from a cooling output of oneof the input beam modules. Each input receptacle is configured to acceptone of the input beam modules. Each input receptacle includes, consistsessentially of, or consists of (i) an electrical output for supplyingelectrical power, (ii) an optical receiver for receiving one or moreinput beams from an input beam module, and (iii) an alignment featurefor mechanically aligning an input beam module with the enclosure,whereby, when an input beam module is accepted within the input beamreceptacle, the electrical output is electrically connected to theelectrical interface of the input beam module and the optical receiveris optically aligned with the optical interface of the input beammodule. The plurality of optical elements receives input beams from theoptical receivers of the input receptacles, combines the input beamsinto a combined output beam, and transmits the combined output beam tothe beam output.

Embodiments of the invention may include one or more of the following inany of a variety of combinations. The beam output may include, consistessentially of, or consist of an output receptacle for receiving anoptical fiber. An optical fiber may be coupled to the beam output. Thebeam output may include, consist essentially of, or consist of a window(e.g., an opening or a solid member substantially transparent to theoutput beam) for transmitting a free-space output beam. One or more, oreven all, of the laser beam sources may include, consist essentially of,or consist of a diode bar configured to emit a plurality of laser beams.The plurality of optical elements disposed within the enclosure mayinclude, consist essentially of, or consist of (i) focusing optics forfocusing input beams onto a dispersive element, (ii) a dispersiveelement for receiving and dispersing the received focused input beams,and (iii) a partially reflective output coupler positioned to receivethe dispersed beams, transmit a portion of the dispersed beamstherethrough as the combined output beam, and reflect a second portionof the dispersed beams back toward the dispersive element. The pluralityof optical elements disposed within the enclosure may include, consistessentially of, or consist of focusing optics for focusing input beamsonto or proximate the beam output. The dispersive element may include,consist essentially of, or consist of a diffraction grating (e.g., atransmissive grating or a reflective grating). The optical elements maybe configured to combine the input beams into the combined output beamand transmit the combined output beam to the beam output even if one ormore of the input receptacles is empty. The laser system may include acontrol system configured to control flow of heat-exchange fluid througheach of the heat-exchange interfaces. The control system may beconfigured to control the flow of heat-exchange fluid based at least inpart on a sensed temperature of each of the input beam modules. Theoptical interface of at least one of the input beam modules may include,consist essentially of, or consist of a window, prism, and/or lens. Theoptical receiver of at least one of the input receptacles may include,consist essentially of, or consist of a window, prism, and/or lens.

These and other objects, along with advantages and features of thepresent invention herein disclosed, will become more apparent throughreference to the following description, the accompanying drawings, andthe claims. Furthermore, it is to be understood that the features of thevarious embodiments described herein are not mutually exclusive and mayexist in various combinations and permutations. As used herein, the term“substantially” means±10%, and in some embodiments, ±5%. The term“consists essentially of” means excluding other materials thatcontribute to function, unless otherwise defined herein. Nonetheless,such other materials may be present, collectively or individually, intrace amounts. Herein, the terms “radiation” and “light” are utilizedinterchangeably unless otherwise indicated. Herein, “downstream” or“optically downstream,” is utilized to indicate the relative placementof a second element that a light beam strikes after encountering a firstelement, the first element being “upstream,” or “optically upstream” ofthe second element. Herein, “optical distance” between two components isthe distance between two components that is actually traveled by lightbeams; the optical distance may be, but is not necessarily, equal to thephysical distance between two components due to, e.g., reflections frommirrors or other changes in propagation direction experienced by thelight traveling from one of the components to the other.

BRIEF DESCRIPTION OF THE DRAWINGS

In the drawings, like reference characters generally refer to the sameparts throughout the different views. Also, the drawings are notnecessarily to scale, emphasis instead generally being placed uponillustrating the principles of the invention. In the followingdescription, various embodiments of the present invention are describedwith reference to the following drawings, in which:

FIG. 1 is a schematic diagram of a conventional diode-based lasersystem;

FIG. 2 is a schematic diagram of a high-power laser system havingmodular beam sources in accordance with embodiments of the presentinvention; and

FIG. 3 is a partial schematic of elements of a beam-combining enclosurein accordance with embodiments of the present invention.

DETAILED DESCRIPTION

FIG. 1 is a schematic diagram of a conventional diode-based laser system100. As shown, multiple individual beam sources 105 are tightlyintegrated within a system enclosure 110 and with a cooling system 115that flows coolant (e.g., water) through each beam source 105. The beamsources 105 are mounted within the enclosure 110 such that they arehighly aligned with lenses 120 that focus the beams toward a beamcombiner 125, which then outputs a combined output beam 130. As shown inFIG. 1, removal and replacement of any individual beam source 105requires disruption of the cooling system 115 for all of the remainingsources 105, as well as time-consuming alignment between the replacementsource 105 and the lenses 120 within the system enclosure 110.

FIG. 2 is a schematic diagram of a high-power laser system 200 havingmodular beam sources in accordance with embodiments of the presentinvention. As shown, the laser system 200 features a beam-combiningenclosure 210, a heat-exchange manifold 215, and multiple input beammodules 220. Each of the input beam modules 220 features a laser beamsource 225 (e.g., a single beam source such as a laser diode, or amultiple-beam source such as a diode bar) disposed within a housing 230,as well as various structures facilitating interfacing with thebeam-combining enclosure 210 and the heat-exchange manifold 215. Invarious embodiments of the invention, each input beam module 220 mayinclude therewithin one or more focusing optics 235 (e.g., one or moreoptical elements such as cylindrical and/or spherical lenses) thatreceive and focus the beam(s) emitted by the laser diode source.

As shown, each input beam module 220 may connect mechanically,electrically, and optically with one of multiple input receptacles 240disposed in or on (or forming portions of) the beam-combining enclosure210. Electrical connections between the input beam modules 220 and thebeam-combining enclosure 210 may be facilitated via an electricalinterface 245 disposed on the input beam module housing 230 thatelectrically connects to a complementary electrical output within aninput receptacle 250 on the beam-combining enclosure 210 when the beammodule 220 is received therein. For example, the input beam moduleelectrical interface 245 and the electrical output 250 may include,consist essentially of, or consist of wires, oppositely polarized (i.e.,male and female) electrical connectors, bump bonds, or otherelectrically conductive structures. Each input beam module 220 may alsoinclude an optical interface 255 (e.g., one or more optical elements,lenses, prisms, and/or windows) through which the focused input beam istransmitted to the beam-combining enclosure 210. Mechanical alignment ofthe various input beam modules 220 to the input receptacles 240 of thebeam-combining enclosure 210 may be facilitated by alignment features(e.g., sockets, protrusions, fasteners, clasps, etc.) shaped to receiveand secure (e.g., latch or compressively retain) the input beam module220 in an orientation in which optical and electrical interconnection ofthe input beam module 200 and beam-combining enclosure 210 result. Eachinput receptacle 240 may also include an optical receiver 260 (e.g., oneor more optical elements, lenses, prisms, and/or windows) that receivesthe input beam from the input beam module 220 when the input beam module220 is connected to the input receptacle 240. In various embodiments,the use of input receptacles obviates the need to utilize optical fiberor other separate connectors between the input beam modules 220 (and/orthe beam sources therein) and the beam-combining enclosure 210.

In various embodiments, the beam-combining enclosure 210 also includes again medium for the formation and/or enhancement of optical gain foreach of the beams emitted from the input beam modules 220. The gainmedium may include, consist essentially of, or consist of one or morematerials which, when excited by the beam(s) from input beam modules220, undergoes stimulated emission. For example, the gain medium mayinclude, consist essentially of, or consist of one or more crystalsand/or glasses doped with one or more ions (e.g., rare-earth ions suchas neodymium, ytterbium, or erbium or transition metal ions such astitanium or chromium), e.g., yttrium aluminum garnet (Y₃Al₅O₁₂), yttriumorthovanadate (YVO₄), sapphire (Al₂O₃), or cesium cadmium bromide(CsCdBr₃). Example gain media include Nd:YAG (neodymium-doped yttriumaluminum garnet), Yb:YAG (ytterbium-doped YAG), Yb:glass, Er:YAG(erbium-doped YAG), or Ti:sapphire used in the form of solid pieces oroptical glass fibers.

In accordance with various embodiments, the beam-combining enclosure 210contains one or more optical elements 262 that receive, from the opticalreceivers 260, the input beams emitted by the input beam modules 220 andcombine the input beams into a combined (e.g., multi-wavelength) outputbeam 265. As shown, the output beam 265 may be coupled into an opticalfiber 270. Once in-coupled into the optical fiber 270, the output beam265 may be utilized to process (e.g., cut, weld, anneal, drill, etc.) aworkpiece.

Importantly, in various embodiments the optical element(s) 262 withinthe beam-combining enclosure 210 combine the input beams of however manyinput beam modules 220 are present on the beam-combining enclosure 210,regardless of whether one or more of the input receptacles 240 is empty.For example, there may be an optical element 262 (e.g., one or moremirrors and/or lenses) associated with each of the input receptacles 240and configured to direct an input beam therefrom to a common focal point(where another optical element 262 may be disposed) where all inputbeams are combined into a output beam 265. In various embodiments,controller 290 may shift and/or rotate one or more optical elements 262associated with empty input receptacles 240 so that no stray light isdirected thereby toward or into the combined output beam 265, via, e.g.,one or more stepper motors, lead screws, and/or rotatable platformsassociated with the optical elements 262. The controller 290 may detectwhether or not an input receptacle 240 is empty or occupied via, e.g., amechanical switch, an optical arrangement (e.g., including a lightsource directed across the input receptacle 240 and a photodetector thatdetects when the light beam from the light source is broken when aninput beam module is present in the receptacle), or other detectortriggered when a module 220 is inserted into or removed from an inputreceptacle 240.

The output beam may be emitted via a beam output element 275 (e.g., anoptical element such as one or more lenses, and/or one or more windows)disposed in or on the beam-combining enclosure 210. In variousembodiments, the beam output element 275 may include, consistessentially of, or consist of a window or opening for emitting afree-space output beam 265, or, e.g., a receptacle that connects tooptical fiber 270, thereby producing a fiber-coupled output. Thecombined output beam may then be utilized for, e.g., materialsprocessing such as cutting or welding.

In various embodiments of the invention, the combining optical elements262 within the beam-combining enclosure 210 may include, for example,various optical elements and lenses, a dispersion element (e.g., adiffraction grating) for dispersing the beams from the individualsources, and a partially reflective output coupler for receiving thedispersed beams and outputting the combined output (i.e., an output beamcomposed of the multiple wavelengths emitted by the individual diodesources). FIG. 3 depicts a partial schematic of various optical elementsthat may be present within the beam-combining enclosure 210. In theembodiment depicted in FIG. 3, an input beam module 220 features a diodebar having four beam emitters emitting beams 310 (see magnified inputview 315), but embodiments of the invention may utilize individual diodeor other laser sources, diode bars emitting any number of individualbeams, and/or two-dimensional arrays or stacks of diodes or diode bars.In view 315, each beam 310 is indicated by a line, where the length orlonger dimension of the line represents the slow diverging dimension ofthe beam, and the height or shorter dimension represents the fastdiverging dimension. As discussed above, the input beam module may emitits beam(s) through optical interface 255. One or more optical elements325 (e.g., transform optics), which may include, consist essentially of,or consist of one or more cylindrical or spherical lenses and/ormirrors, are used to combine each beam 310 along a WBC direction 330.Each optical element 325 may correspond to an optical receiver 260 andbe associated with a single input beam module 220, and/or one or moreoptical elements 325 may receive the input beams from the opticalreceivers 260. The optical elements 325 then direct and/or overlap thecombined beam onto a dispersive element 335 (which may include, consistessentially of, or consist of, e.g., a diffraction grating such as areflective or transmissive diffraction grating), and the combined beamis then transmitted as single output profile onto an output coupler 340(which may correspond to beam output element 275). The output coupler340 then transmits the combined output beam 265 as shown on the outputfront view 350. The output coupler 340 is typically partially reflectiveand acts as a common front facet for all the laser elements in thisexternal cavity system. An external cavity is a lasing system where thesecondary mirror is displaced at a distance away from the emissionaperture or facet of each laser emitter. In some embodiments, additionaloptics are placed between the emission aperture or facet and the outputcoupler or partially reflective surface. The output beam 265 may becoupled into optical fiber 270 and/or utilized for applications such aswelding, cutting, annealing, etc. Although FIG. 3 depicts beam combiningfor only one input beam module 220 from which multiple beams areemitted, one or more of the optical elements within the beam-combiningenclosure 210 (e.g., optical element 325 and/or dispersive element 335)may receive one or more beams from one or more additional input beammodules 220 so that such beams are also combined into output beam 265.In addition, FIG. 3 depicts an embodiment in which the input beams fromthe various input beam modules 220 are combined via WBC into a commonmulti-wavelength output beam 265; in other embodiments, the beams fromthe input beam modules 220 are simply spatially overlapped into outputbeam 265 without the use of WBC.

In various embodiments of the invention, the heat-exchange manifold 215circulates cooling fluid to the input beam modules 220 to prevent theinput beam modules 220 from heating to excessive or damagingtemperatures during operation. The heat-exchange manifold 215 mayinclude, or may be in fluid connection with, a reservoir 280 of coolingfluid. The reservoir 280 and/or the heat-exchange manifold 215 mayincorporate or be in thermal contact with, for example, one or more heatexchangers for cooling the cooling fluid prior to the cooling fluidbeing supplied to the input beam modules 220 and after heated fluid isreceived from the input beam modules 220. As shown, the heat-exchangemanifold 215 also includes multiple heat-exchange interfaces 285 eachconnected to one of the input beam modules 220. Each of theheat-exchange interfaces 285 may include, consist essentially of, orconsist of, e.g., an input conduit 286 for receiving “spent” or heatedfluid from the input beam module 220 and an output conduit 287 forsupplying cool fluid to the input beam module 220. The input and outputconduits 286, 287 may interface with cooling inputs 288 and outputs 289(e.g., openings and/or conduits) disposed on each of the input beammodules 220, thereby forming a recirculation loop for the cooling fluidthat extends from the heat-exchange manifold 215, to each of the inputbeam modules 220, and back to the heat-exchange manifold 215 (and/or tothe reservoir 280 and/or to one or more heat exchangers). In variousembodiments of the invention, the input 288 and output 289 on one ormore of the input beam modules fluidly connect to a heat-managementpackage (e.g., anode and/or cathode coolers) for the beam source 225 asdescribed in U.S. patent application Ser. No. 15/627,917, filed on Jun.20, 2017, the entire disclosure of which is incorporated by referenceherein.

Exemplary cooling fluids that may be utilized in accordance withembodiments of the present invention include water, glycols, or otherheat-exchange fluids. The degree of cooling provided by theheat-exchange manifold 215 may be based on the number of installed inputbeam modules 220, or may depend on monitored temperature (e.g., of oneor more installed input beam modules 220) in a feedback configuration.For example, each of the input beam modules 220 and/or input receptacles240 may incorporate therewithin a temperature sensor (e.g., athermistor, thermometer, thermocouple, etc.), and a controller (or“control system”) 290 (which is operatively coupled to all or a portionof heat-exchange manifold 215 and/or to one or more other components ofsystem 200) may control the flow of cooling fluid through theheat-exchange manifold 215 based at least in part on the sensedtemperature. For example, the controller 290 may control one or morevalves, which may each be associated with one or more of theheat-exchange interfaces 285, to open or close based on the sensedtemperature of one or more of the input beam modules 220 and/or the beamsources therewithin. The controller 290 may also control one or morepumps and/or valves that determine the flow rate of heating fluidthrough the heat-exchange manifold 215 and/or the temperature of coolingfluid in reservoir 280 based at least in part on the sensedtemperature(s).

The controller 290 may be provided as either software, hardware, or somecombination thereof. For example, the system may be implemented on oneor more conventional server-class computers, such as a PC having a CPUboard containing one or more processors such as the Pentium or Celeronfamily of processors manufactured by Intel Corporation of Santa Clara,Calif., the 680x0 and POWER PC family of processors manufactured byMotorola Corporation of Schaumburg, Ill., and/or the ATHLON line ofprocessors manufactured by Advanced Micro Devices, Inc., of Sunnyvale,Calif. The processor may also include a main memory unit for storingprograms and/or data relating to the methods described above. The memorymay include random access memory (RAM), read only memory (ROM), and/orFLASH memory residing on commonly available hardware such as one or moreapplication specific integrated circuits (ASIC), field programmable gatearrays (FPGA), electrically erasable programmable read-only memories(EEPROM), programmable read-only memories (PROM), programmable logicdevices (PLD), or read-only memory devices (ROM). In some embodiments,the programs may be provided using external RAM and/or ROM such asoptical disks, magnetic disks, as well as other commonly used storagedevices. For embodiments in which the functions are provided as one ormore software programs, the programs may be written in any of a numberof high level languages such as FORTRAN, PASCAL, JAVA, C, C++, C#,BASIC, various scripting languages, and/or HTML. Additionally, thesoftware may be implemented in an assembly language directed to themicroprocessor resident on a target computer; for example, the softwaremay be implemented in Intel 80x86 assembly language if it is configuredto run on an IBM PC or PC clone. The software may be embodied on anarticle of manufacture including, but not limited to, a floppy disk, ajump drive, a hard disk, an optical disk, a magnetic tape, a PROM, anEPROM, EEPROM, field-programmable gate array, or CD-ROM.

In the event of failure of or damage to one of the laser sources 225 orinput beam modules 220, the operator of the laser system 200 may simplyunplug the affected input beam module 220 from the beam-combiningenclosure 210 and disconnect the input beam module 220 from theheat-exchange manifold 215, and replace the faulty input beam module 220with a replacement input beam module 220. The presence of amalfunctioning input beam module 220 (and/or the absence of one or moreinput beam modules 220 from various input receptacles 240) does notaffect overall operation of the beam-combining enclosure 210 beyondreducing overall output power. The various interfaces and connectionfeatures of the beam-combining module 210, the heat-exchange manifold215, and the input beam modules 220 facilitates rapid replacement of theinput beam modules 220 during deployment of the laser system 200 by theend user. Thus, laser systems in accordance with embodiments of thepresent invention are more reliable and less expensive to maintain thanconventional high-power laser systems. Moreover, since only the inputbeam modules 220 require replacement in the event of failure of one ormore of the input beam sources 225, the remaining components of thelaser system 200 need not be moved or shipped to a supplier for repairin the event of a failure.

The terms and expressions employed herein are used as terms ofdescription and not of limitation, and there is no intention, in the useof such terms and expressions, of excluding any equivalents of thefeatures shown and described or portions thereof, but it is recognizedthat various modifications are possible within the scope of theinvention claimed.

What is claimed is:
 1. A laser system for combining a plurality of inputbeams into a combined output beam, the laser system comprising: anenclosure comprising a beam output for outputting the combined outputbeam; a heat-exchange manifold comprising (i) a reservoir for containingheat-exchange fluid, and (ii) a plurality of heat-exchange interfaceseach comprising (a) an output conduit for supplying heat-exchange fluidand (b) an input conduit for receiving heat-exchange fluid; a pluralityof input beam modules, each input beam module comprising (i) a housing,(ii) a laser beam source disposed within the housing, (iii) disposedwithin the housing, a focusing optical element for receiving andfocusing one or more input beams emitted by the laser beam source, (iv)disposed on the housing, an optical interface for transmitting thefocused one or more input beams out of the housing, (v) disposed on thehousing, an electrical interface for transmitting electrical power intothe housing and to the laser beam source, and (vi) a cooling interfacecomprising (a) a cooling input for receiving heat-exchange fluid fromone of the output conduits of the heat-exchange manifold and disposingthe heat-exchange fluid in thermal contact with the laser beam sourceand (b) a cooling output for receiving heat-exchange fluid from thelaser beam source after heat exchange therebetween and outputting theheat-exchange fluid to an input conduit of the heat-exchange manifold;disposed on the enclosure, a plurality of input receptacles, each inputreceptacle configured to accept one of the input beam modules, whereineach input receptacle comprises (i) an electrical output for supplyingelectrical power, (ii) an optical receiver for receiving one or moreinput beams from an input beam module, and (iii) an alignment featurefor mechanically aligning an input beam module with the enclosure,whereby, when an input beam module is accepted within the input beamreceptacle, the electrical output is electrically connected to theelectrical interface of the input beam module and the optical receiveris optically aligned with the optical interface of the input beammodule; and disposed within the enclosure, a plurality of opticalelements for receiving input beams from the optical receivers of theinput receptacles, combining the input beams into a combined outputbeam, and transmitting the combined output beam to the beam output. 2.The system of claim 1, wherein the beam output comprises an outputreceptacle for receiving an optical fiber.
 3. The system of claim 1,wherein the beam output comprises a window for transmitting a free-spaceoutput beam.
 4. The system of claim 1, wherein one or more of the laserbeam sources comprises a diode bar configured to emit a plurality oflaser beams.
 5. The system of claim 1, wherein the plurality of opticalelements disposed within the enclosure comprises (i) focusing optics forfocusing input beams onto a dispersive element, (ii) a dispersiveelement for receiving and dispersing the received focused input beams,and (iii) a partially reflective output coupler positioned to receivethe dispersed beams, transmit a portion of the dispersed beamstherethrough as the combined output beam, and reflect a second portionof the dispersed beams back toward the dispersive element.
 6. The systemof claim 5, wherein the dispersive element comprises a diffractiongrating.
 7. The system of claim 1, wherein the optical elements areconfigured to combine the input beams into the combined output beam andtransmit the combined output beam to the beam output even if one or moreof the input receptacles is empty.
 8. The system of claim 1, furthercomprising a control system configured to control flow of heat-exchangefluid through each of the heat-exchange interfaces.
 9. The system ofclaim 8, wherein the control system is configured to control the flow ofheat-exchange fluid based at least in part on a sensed temperature ofeach of the input beam modules.
 10. The system of claim 1, wherein theoptical interface of at least one of the input beam modules comprises atleast one of a window, prism, or lens.
 11. The system of claim 1,wherein the optical receiver of at least one of the input receptaclescomprises at least one of a window, prism, or lens.
 12. A laser systemfor combining a plurality of input beams emitted by a plurality of inputbeam modules into a combined output beam, wherein each of the input beammodules comprises (i) a housing, (ii) a laser beam source disposedwithin the housing, (iii) disposed within the housing, a focusingoptical element for receiving and focusing one or more input beamsemitted by the laser beam source, (iv) disposed on the housing, anoptical interface for transmitting the focused one or more input beamsout of the housing, (v) disposed on the housing, an electrical interfacefor transmitting electrical power into the housing and to the laser beamsource, and (vi) a cooling interface comprising (a) a cooling input forreceiving heat-exchange fluid and disposing the heat-exchange fluid inthermal contact with the laser beam source and (b) a cooling output forreceiving heat-exchange fluid from the laser beam source after heatexchange therebetween and outputting the heat-exchange fluid, the lasersystem comprising: an enclosure comprising a beam output for outputtingthe combined output beam; a heat-exchange manifold comprising (i) areservoir for containing heat-exchange fluid, and (ii) a plurality ofheat-exchange interfaces each comprising (a) an output conduit forsupplying heat-exchange fluid to a cooling input of one of the inputbeam modules and (b) an input conduit for receiving heat-exchange fluidfrom a cooling output of one of the input beam modules; disposed on theenclosure, a plurality of input receptacles, each input receptacleconfigured to accept one of the input beam modules, wherein each inputreceptacle comprises (i) an electrical output for supplying electricalpower, (ii) an optical receiver for receiving one or more input beamsfrom an input beam module, and (iii) an alignment feature formechanically aligning an input beam module with the enclosure, whereby,when an input beam module is accepted within the input beam receptacle,the electrical output is electrically connected to the electricalinterface of the input beam module and the optical receiver is opticallyaligned with the optical interface of the input beam module; anddisposed within the enclosure, a plurality of optical elements forreceiving input beams from the optical receivers of the inputreceptacles, combining the input beams into a combined output beam, andtransmitting the combined output beam to the beam output.
 13. The systemof claim 12, wherein the beam output comprises an output receptacle forreceiving an optical fiber.
 14. The system of claim 12, wherein the beamoutput comprises a window for transmitting a free-space output beam. 15.The system of claim 12, wherein the plurality of optical elementsdisposed within the enclosure comprises (i) focusing optics for focusinginput beams onto a dispersive element, (ii) a dispersive element forreceiving and dispersing the received focused input beams, and (iii) apartially reflective output coupler positioned to receive the dispersedbeams, transmit a portion of the dispersed beams therethrough as thecombined output beam, and reflect a second portion of the dispersedbeams back toward the dispersive element.
 16. The system of claim 15,wherein the dispersive element comprises a diffraction grating.
 17. Thesystem of claim 12, wherein the optical elements are configured tocombine the input beams into the combined output beam and transmit thecombined output beam to the beam output even if one or more of the inputreceptacles is empty.
 18. The system of claim 12, further comprising acontrol system configured to control flow of heat-exchange fluid througheach of the heat-exchange interfaces.
 19. The system of claim 18,wherein the control system is configured to control the flow ofheat-exchange fluid based at least in part on a sensed temperature ofeach of the input beam modules.
 20. The system of claim 12, wherein theoptical receiver of at least one of the input receptacles comprises atleast one of a window, prism, or lens.